What is your current mpg

[ldsman]

I have set a goal for my mk4 build. My goal is to have 400 hp and get 30 mpg. Not sure how much work will be involved to do this but i was wondering what people are geting in their 4.6 set ups.

[Cobradavid]

I have a stock 4.6 SOHC from a 2001 GT, T3650 transmission and 3.27 gears. I average ~18 mpg around town and ~22-24 mpg on the highway.

30 mpg seems to be a pretty lofty goal. My Mazda3 (2.0L four-banger, 5 speed manual) gets 29-30mpg around town and 35 mpg on the highway.

David

[mybigbrain]

i have a stock mach 1, auto 3.27 rear end and i get 22-24 mpg on the freeway.
thats only if i'm not driving like a crazzy person.

[ACLR8R]

Originally Posted by mybigbrain

i have a stock mach 1, auto 3.27 rear end and i get 22-24 mpg on the freeway.
thats only if i'm not driving like a crazzy person.

Wow, I was hoping for better than that as well! I have a 98 cobra DOHC, 5 speed, and 3.27's.

I know its not as aerodynamic, but my C5 gets 31mpg hwy with a mild cam and 385rwhp.

[AZPete]

4.6 SOHC, T45, 3:27 IRS
Over 5,000 miles I tracked mpg at each fill-up. Minimum was 17.5, maximum was 22.5
Good luck getting 30 mpg
Pete

[krhayden]

4.6 SOHC, T45, 3.27
10000 miles and I consistently average between 19 and 23 depending on how I drive.

[icemanzx7]

2003 4.6 DOHC Cobra Engine. 600RWHP, Consistant 23MPG, as long as I'm cruising. But it's still is pretty efficient while driving aggressive, 17MPG.

[ClemsonS197]

If you want 400hp and 30mpg better switch to a coyote.

[hala514]

or a turbo V6....

Ford F-150 Getting 400 HP EcoBoost V6

23mpg in an F150 should easily get 30mpg in a roadster.

[beeman]

...or extensive aero mods. Place a brick in a wind tunnel, would probably look a lot like the ffr.

[rick8928]

Or find a strictly downhill route. Otherwise, not going to happen unless you eliminate the performance (e.g. go to skinny/hard tires, silly gearing, ride height reduction, low slung spoilers, modifications to body bulges, ......). In which case, why build a Cobra?

[Bill Hughes]

Too much frontal area and too high a drag coef. Better off to build a coupe.

My best MPG to date was 22 mpg

[niceguy]

I really don't care about mpg on my cobra, when it gets to qtr tank I stop and fill it up. I got my cobra to drive... I have my daily driver for mpg.

[MPTech]

Smiles per gallon is more important.

If I get more than 20 mpg, it means I'm not having fun!

[Bob Gruen]

Originally Posted by ACLR8R

I know its not as aerodynamic, but my C5 gets 31mpg hwy with a mild cam and 385rwhp.

C5 Corvette? The C5 corvette is a pretty slippery car. Coef of drag From Corvette Fever:

C5=.334, C6=.343. In terms of drag they measured how much HP it took to reach 100 MPH. The numbers were: C5=128.6, C6=133.0

As far as the original poster...

There should be a pretty obvious problem of creating HP and preserving MPG, as in the two are in direct odds with each other. City mileage favors mass more, in which the FF cars do well, while highway is more related to drag. Expanding an engine's capability to generate peak horsepower is always going to remove it from the it's effeciency sweet spot and lower the MPG.

I would love to see someone build a Cobra with one of the modern 300+ HP V6s from Ford or Chevy. These engines are using all the latest technologies to get a staggering ~30 MPG in big 4 seater coupes, imagine what they could do in an ultra lightweight Cobra build. Going with a V6, a T5 Tranny, and possibly a Ford 8" rear eng with a Currie center section (saves 70 lbs over a 9") might shave more than 200 pounds off of an already flyweight car... From there you might do performance upgrades to trade MPG for more HP, but these engines are already so high tech and effecient that there might not be too much more to be had besides capacity expansion.

Bob

[Danner]

I'm going to be attempting 400hp and near 30mpg from a 347 windsor, megasquirt 3 lean burn, a T56, and a 3.07 rear-end. I've got the 400hp, and I should be able to spin very low RPM in 6th gear at highway speeds.

I'll certainly be posting about this when all is complete.

[Big Blocker]

Build your car with an electric motor . . . 30 Mpg very possible . . .

My signature line gets me 23 on the open road.

Doc

[Bill Hughes]

Where do you put the gallons into an electric motor? A gas powered generator to power the electric motor?

[MarkT]

Maybe one of the moderators should move this thread to hipermiling forum…

[Driver_WT]

Originally Posted by Bob Gruen

C5 Corvette? The C5 corvette is a pretty slippery car. Coef of drag From Corvette Fever:

C5=.334, C6=.343. In terms of drag they measured how much HP it took to reach 100 MPH. The numbers were: C5=128.6, C6=133.0

Bob

My 2005 C6 Corvette got 32 mpg at steady 75 mph (stock except for Vararam CAI, ported intake manifold, Magnaflow cat back, and a very nice computer tune) - approx. 440 hp, 3.42 gears and six speed manual trans. 3180 lbs. (about the same highway mpg as my 2005 Civic 1.7 liter)

My 2008 C6 Corvette gets 28 to 29 mpg at steady 75 mph (Haltech CAI, computer tune, GM bimode exhaust) - approx. 450 hp, 3.42 gears and six speed manual trans. 3200 lbs

Some of this is due to coeff of drag advantage, but the LS2 and LS3 engines are very efficient engines, lots of overdrive in the trans, and the engines respond well to a tune and minor mods (especially the LS2)

[Bob Gruen]

Exactly...

It's not a linear function, but if it takes 133 HP to get your C6 to reach 100 mph, what would it be to hold 70 mph? 90~100 HP? Less? A Cobra coef of drag is no where near the C5s or C6s. The front swallows a bunch of air then forces it under the car while the windshield has a lot in common with the one on my Wrangler. One big MPG mod would be to swap out the windshield for a Challenge windscreen, but this isn't a very practical solution.

The adiabatic efficiency of an engine (how much of the fuel's heat is actually converted to kinetic energy) largely has to do with compression ratio, but other issues like the mass of the rotating assembly and flame front propagation (as it effects ignition timing) can have a substantial effect as well.

30 MPG in a Cobra is definately possible, but I do think it will take a lot of the latest engine technology to maintain that MPG performance while moving the peak HP up to the levels that some on this thread are seeking (as in the high feature V6s). Is the combination of direct fuel injection, varaible valve timing, and drive by wire appearing on any American V8s yet?

Failing that I think I'd approach it using small displacement & high RPM's to make HP. A centered sparkplug (3 or 4 valve) modular V8 with the smallest displacement and lightest pistons and rods available and a really good ECU with sequential fuel injection and an adjustable reaction to engine knock as I would want to push the compression ratio up (probably Electromotive TEC). Probably try to get it to a 8000 RPM redline. I'd also probably vent the engine bay to the sides of the car by enlarging and reshaping the side vents.

None of this is cheap, which is why the high feature V6s are attractive for power and economy (but completely non-traditional). Ford has added airbags in the seats of the Mustang, which means that they will be totaled with much less actual damage as just the airbag deployment is a costly repair. Do a google search on "2013 Mustang V6 salvage" to see the condition on some of these 'totaled' cars...

Bob

[conmech]

Time for a Gear Vendor

Gear Vendors under/overdrive transmissions the most awarded auxiliary transmissions.

[Tickwomp]

Maybe you should have gotten a Miata;-)

Just kidding of course!

[04SVTCobra]

Mid 20's on the HWY

[R Edgar]

Originally Posted by ldsman

I have set a goal for my mk4 build. My goal is to have 400 hp and get 30 mpg. Not sure how much work will be involved to do this but i was wondering what people are geting in their 4.6 set ups.

I am willing to bet, if you accomplish your goal of having a Cobra that gets 30 mpg on the highway, you will never actually be able to do it. Remember you have a right foot and everyone that I know likes to use theirs.

Roy from Springboro

[ACLR8R]

Originally Posted by Bob Gruen

Exactly...


Is the combination of direct fuel injection, varaible valve timing, and drive by wire appearing on any American V8s yet?

Bob

There is, the new LT1. Give it some time and that might be a viable option. Would love to do a 33 hot rod with an LT1 in a year or two!